Abstract

PIP: Some properties of specific progestogen binding activity in the human cervix are described. High cytosol affinity was observed for progesterone and synthetic progestagens, but not for corticosteroids or norethindrone, medroxyprogesterone acetate, chlormadinone acetate, progesterone, 5alpha-pregnane-3,20-dione, norethindrone acetate, 17alpha-hydroxyprogesterone, cortisol, and estradiol. Progesterone binding in cytosols with high concentrations of CBG-like contaminants had a dissociation rate constant of 6.9 X 10(-5)s(-1). Ka values were similar for binding sites throughout the cervix, with concentrations being highest in the region around the columnar epithelium. Concentrations of binding sites per mg DNA were similar in the columnar epithelium and stroma, but higher in the squamous epithelium. Progesterone binding to endometrial tissue was greater than that for the corresponding cervix. Mean concentrations per mg were markedly higher during the proliferative phase than the secretory phase of the menstrual cycle, though this difference in terms of concentrations per mg DNA was significant only for cervical cytosols.